Article coating method

ABSTRACT

AN APPARATUS AND METHOD FOR COATING ARTICLES OR SUBSTRATES, PARTICULARLY RAZOR BLADES OR OTHER CUTTING INSTRUMENTS, IN WHICH MEANS ARE PROVEDED FOR ESTABLISHING A RADIO FREQUENCY ALTERNATING ELECTRICAL FIELD BETWEEN ELECTRODES WITHIN A VACUUM CHAMBER FOR SPUTTERING A COATING FROM A TARGET HAVING THE COATING MATERIAL THEREON TO THE ARTICLE, OR SUBSTRATE TO BE COATED. THE DESCRIBED APPARaTUS INCLUDES MEANS FOR PROVIDING PRELIMINARY CLEANING OF THE SUBSTRATE AS WELL AS THE TARGET BEFORE COATING, SUCH CLEANING OPERATION BEING CAPABLE OF OPERATING IN ANY ONE OF SEVERAL DIFFERENT OPERATIONAL MODES. VARIOUS MECHANICAL HANDLING AND PROTECTIVE DEVICES ARE DESCRIBED FOR CARRING OUT THE OPERATIONS IN A SINGLE VACUUM CHAMBER. PREFERABLY, THE SUBSTRATE IS FIRST CLEANED BY SO-CALLED REVERSE SPUTTING (USING THE INTENDED SUBSTRATE AS A TARGET) OR GLOW DISCHARGE CLEANING, OR SPUTTING ETCHING, THEN PROTECTED AGAINST CONTAMINATION WHILE THE TARGET IS CLEARED, WITH THE SUBSTRATE THEREAFTER BEING EXPOSED TO COATING BY SPUTTERING. IN ANOTHER EMBODIMENT, SIMULATANEOUS SUBSTRATE CLEANING AND DEPOSITION TAKES PLACE, AS THE TARGET AND THE SUBSTRATE ARE MAINTAINED AT DIFFERENT POTENTIALS WHILE HAVING RADIO FREQUENCY ALTERNATING VOLTAGES IMPRESSED THEREON. THE APPARATUS PROVIDES A MEANS OF PERFORMING THESE OPERATIONS EITHER SIMULTANEOUSLY OR IN SEQUENCE ON A PLURALITY OF ARTICLES AT ONE OR MORE STATIONS WITHOUT BREAKING THE VACUUM IN THE EVACUATED CHAMBER, OR ALLOWING CONTAMINATION OF THE ARTICLE, SUBSTRATE OR TARGET BETWEEN CLEANING AND COATING OPERATIONS.

- March 27, 1973 c; Q LANE ETAL ARTICLE COATING METHOD 5 Sheets-SheetFiled June 1'), 1969 E S H L Y RM S OLRM T T WL T g VGMW N RC H [0 T BYH March 27, 1973 e. c. LANE ET AL ARTICLE COATING METHOD 5 Sheets-Sheet2 Filed June 5, 1969 March 27, 1973 G. c. LANE ET AL ARTICLE COATINGMETHOD 5 Sheets-Sheet 4.

Filed June 5, 1969 March 27, 1973 G. c. LANE ET AL ARTICLE COATINGMETHOD 5 Sheets-Sheet 5 Filed June 3, 1969 r' 3,723,276 Ice PatentedMar- 27, 1973 United States Patent 1 2 3,723,276 Nevertheless, as is thecase with many mass produced A ICLE CQATING METHO articles, there isstill room for further improvement, par- D George C. Lane, Danbury,Cyril A. Cartwright, Monroe, ticularly by way of methods and apparatuswhich make and Keith W. Elmslie, Guilford, Conn., assignors to higherproduction speed and even better quality control Warner-113mm y, MorrisPlains, possible, as well as those which tend to make material Flled i-73 handling and the like simpler and more foolproof. There U S 0 204,192c 9 Claims is also a need for systems which are improved in regard tosimplifying pretreatment of the substrate to be coated and which aifordgreater versatility and reliability in use.

ABSTRACT OF THE DISCLOSURE 10 There is also a need for simplifiedapparatus which make practical the practice of a process having aplurality of An apparatus and method for coating articles or substepswithin a single unit of apparatus.

strates, particularly razor blades or other cutting instruments, inwhich means are provided for establishing a In View of 'E needs Set e itis an Obieet radio frequency alternating electrical field bet of thepresent invention to provide an improved product ween electrodes withina vacuum chamber for sputtering a coating g g ggg ggi' g z g gf gi ggszgg a g appafrom a target having the coating material thereon to thearticle, or substrate to be coated. The described apparatus which P efor Pleamng Substrate Prior coating by sequential or simultaneousoperations carried includes means for providing preliminary cleamng o te out within a single evacuated chamber so that the operasubstrate aswell as the target before coating, such cleaning operation being capableof operating in any one of Hons may be f' i wlthout breekmg the .vacuumseveral different Operational modes various mechanical necessary toobtain conditions under which sputtering takes handling and protectivedevices are described for carrying out the operations in a single vacuumchamber. Prefere obleet 15 PYeVlde e apparatus cleaning ably, thesubstrate is first cleaned by so-calle revel-Se an article to be coated,for cleaning the target which serves sputtering (using the intendedsubstrate as a target) or as a Source glow discharge cleaning, orsputter etching, then protected against contamination while the targetis cleaned, with the substrate thereafter being exposed to coating bysputtering. In another embodiment, simultaneous substrate cleaning anddeposition takes place, as the target and the substrate are maintainedat different potentials while having radio frequency alternatingvoltages impressed thereon. The apparatus provides a means of performingthese the blade to a h g Vacuum m operations either simultaneously or insequence on a p ue e l of the mventlen 15 9 PYOVlde an effp rality ofarticles at one or more stations without breaking Yams 1n Whleh ereverse eputtefmg y be ut lhled the vacuum in the evacuated chamber, orallowing as amethed of cleaning the article to be coated prior totamination of the article, substrate or target between eoalmg thereo?cleaning and coating operations. Another object is to provide anapparatus in which cleaning of an article or substrate by glowdischarge, or

of coating material while simultaneously protecting the article fromcontamination by the material cleaned from the target, and thereaftercoating the article by exposing it to coating material sputtered fromthe tar- 0 reverse sputtering, a sputter etching may be carried out, BAKGRO OF THE INVENTION followed by coating the same article or substratewith a It is we known that it is highly desirable, in the sputteredcoating material, all being carried out within terest of durability andeconomy, to obtain extremely thin, the Same apparatushighly purecontinuous metal, alloy, or like hard coating by v v g g fira ggst Sieth;1 lfsllvcaltiar algal: gig/322a; (111133;);

on the sharpened edges of cutting instruments such as i conditions ofhigh vacuum without breaking the vacuur between steps of the method.

to cutting surfaces such as blade or knife edges are now b1 ge gg g ezlgsfig il l stlli gigs gfirgpggg sgl gg tg u ethods and a aratus beindescribe u 2 known S ch as m pp g be coated in the same atmosphere, andmay be protectr t' n Ser Nos. 680,794, and 680,- for example m apphca 105 against atmospheric or like contamination between clea 926, both filedNov. 6, 1967. (Ending instruments made ing and coating.

in this manner possess coatings of about 50 to 800 angstrorns (A.) andpreferably 100 to Ziflt) A., which are thick g sg i ggg b ga g g ggil gz z g z gi z enough to protect the cuttmg edge mm premature wear andcoated in a desired sequence, or simultaneously ii and corrosion, butstill thin enough to prevent rapid dullhi h vacuum environment ing ofthe edge of me A Principal adiantage A still further ob'ect is to rovidea cleaning and coat of using the sputtering deposition methods describedin apparatus which iniludes ayacuum chamber means m these applicationsis that the cutting instrument may be in for pp g a plurality ofarticles to {De coated finish ground, honed and stropped to a desireddegree 0 for advancin them in succession ast a coafm Sta sharpness andthereafter coated bprotecgifizh wliitlh a lilar after a fi g Operationis perfgrmed and u u t e e i g rs} 3 3? 222 g 223 3 z g f includes meansfor establishing a high frequency elect a field either alternately orsimultaneously between the or to sharpen an edge previously imparted toan instrumeut after the edge has been hardened. Edge surfaces at and thegroufld and the aftlcles f ceated am so coated may also readily becoated with lubricous coatground for cleemng and eoatmg the article 111the de ing materials such as plastic materials, silicone lubricants,mannernow known A further ob ect of the invention is to provide ai orthe like, in any known manner. It is that articles made with the use ofthe apparatus an paratus in which the means for supporting and m methodsreferred to above possess heretofore unsurpassed the articles to becoated about within the vacuum c ity consistent with reasonable economyand outstandber includes means for maintaining the edges of thc qual inguseful life. cles approximately parallel to a surrounding surfac ing thetime they are being cleaned, and which includes given axis to reversethe orientation thereof at a desired means for rotating one or morearticle holders to a depoint in the apparatus; and sired extent aboutits own axis within a relatively small is a fragmentary plan view of aportion of the portion of the motion cycle of the article holder and forarticle protective device of the invention, showing the olding itagainst axial rotation during a relatively larger mo e of operation andan alternate position thereof in portion of its rotating cycle. phantomlines.

Another Object IS to provide an apparatus IH- OF THE cludes means,preferably single means, for exposing ar- MENTS OF THE INVENTION ticlesto be coated to coating material being sputtered from the target in oneposition of said means, and for pro- 1 The invention l now be d s ribedWith reference tecting the articles against contamination sputtered fromto Partlchlar ehlhodlmems thereof, In h first f which the target durmgcleanmg th f m another posmon f c caning of all the articles to becoated takes place before such means, as well as serving as means foraiding target any of the articles, groups of artlcles, a ate cleaningprior to the time the target material is sputtered F emhg how thedrawings In greater etai and onto the articles to b Coated. particularlyto FIGS. 1 and 2, this form of the invention 0t er object is to providea method in which a radio may be seen to be di in a combination articlerequency 1s Impressed both on a target and on an arm cleaning andcoating apparatus 10 whic is somewhat dicle to be coated, the target andarticle are allowed to agrammahcahy Q t0 1110111618 8 rame or base 12,reach differing electrical potentials so that there is a signifimeans Pestahhshlhfe ah evachated r 8 h rm f cant potential between the two, inwhich minute quantities an exterior, q h hght houslflg Which is mountedof an inert gas are introduced at least into an evacuated means forrecelvlhg and handling arhcles t e c ated, 1n region between thearticles and the target, whereby atoms the form of F assembly 16Comprised of a lower ring ionized by the electrons flowing in thechamber strike stand 18, an Insulator r1113 20 a IOWer earing race 22 acollision of an ionized atom with the article or the target 25 a drive?ring 28 which adapted to Support a P sputtering off one or more surfaceatoms, thereof, to prorahtY P amcle holdhr means the f m 0 bayonet asvide simultaneous lower rate surface cleaning of the arsembheF 30 fholdlhg a plurality of rt s 32 thereon. ticle and higher rate sputteringof the coating onto the ar- The driven rmg 28 mc1udeS external rlhg geteeth 34 ticle, and an apparatus for carrying out the method. adflptedto mesh Wlth the teeth 36 on a P1111011 gear These and other objects ofthe invention are achieved 30 dnven by Stub shaft Eilch bayonet assemblyQ by providing a vacuum apparatus having means for cludeswerticallydisposed tines 42 which are received porting a plurality of articles orgroups or articles within a clrcular holder member 44 havmg a lowerexten an evacuated chamber or other region target means Com sion 46rotatably mounted for iotation in bearings 48 and taining a coatingmaterial, means for moving the articles further Includes a bottom g 50fixedly attached h f about in the chamber, means for supplying highfrequency i 52 .arespmvlded on h gear for recelvmg electrical energy tothe articles for one mode of operation, C am T e 4 also has Pomohsthereof ehgflgmg and to the target In another mode and Control means forteeth 56 on the outer periphery of a central, fixed sprocket causingthese operations to take place simultaneously or 8 mqunted on a hub 60Protected by Insulator 62 from in a desired sequence of Operation toprovide Coated electrical contact therew th. The bearings 48 engage thetides made by the method and apparatus outer surface of a plurality ofsleeves 64 disposed in the 2 y The exact manner in which these and otherob ects of 1 en ring 8 an m use rotation of the mug 28 about of the car50, and conse uent rotat'o f when they are considered in COHJUIICUOHwith the apg q l n 0 each bayonet tation of the ring 28 about its axiscauses rotawhich reference is made to the accompanying drawings, Thus mw erein like reference numerals indicate corresponding of each bayonetassembly 30 about Its Own so t at a given part thereof, for example anedge 66 of the parts throughout b ade or other article 32 held on thebayonet assembly BRIEF DESCRIPTION OF THE DRAWINGS FIG 1 is a verticalsectional View, taken through a alternately for each full revolution ofthe ring 28. In other portion fth vacuum chamber fth apparatus fthwords, t e exterior circumference of the sprockets and vention, andillustrating certain principal portions of the gears 50, 58 may beselected so as to turn the bayonet ,pparams; assembly 30 one-half turnfor each complete turn of the FIG. 2 is a top plan view, partly in planand partly in Tlhg ection, with portions broken away, showing theappara- In the embodiment shown in FIGS- 1 and a motor Us of FIG 1; 68is provided having a shaft 70 thereon containing a driv- FIG 3 is aschematic View of a simplified form of the en bevel gear 74 which isfixedly attached t0 the stub lectrical circuitry of the invention; shaft40. Thus, the ring 28 and the parts associated there- F G. 4 is aschematic view of another portion of the with are rotated by the mannerset forth above. ectrical circuit of the invention showing a power sup-As shown in FIGS. 1 and 2, means are provided for y, an alternatingcurrent source and an impedance protecting the articles 32 held on thebayonets 30 or other atching network; article holding devices againstundesired contamination, F 5 is a schematic view showing the operationof and for assisting in the cleaning of such articles, in the Jortion ofthe electrical circuit of the apparatus in one form of an article shroudassembly 76 defining, on the dc of operation for cleaning the blade;inside thereof, a cylindrical passageway 78. The shroud E is a schematicview showing the circuit of the assembly 76 includes an outer wallportion 80, an inner iaratus in another mode of operation thereof, forcleanwall portion 82, a top wall portion 84, and on an insulatthe bladesor the like by another process; ing support 86 which is fixedly attachedto the roof por- G 7 is a top view, partly in horizontal section, andtion 88 of the chamber 14. The bottom edge 90 of the l portions brokenaway, showing another form of the shroud assembly 76 is closely spacedapart from the iratus of the invention; upper surface of the ring 28, sothat the articles 32 held on is a vertical sectional view, on a greatlyenthe tines of 42 of the bayonets 30 are substantially comis fororienting groups of articles to be coated in a rotation of the ring 28.ed position of use, and for rotating them about a Referring nowparticularly to FIG. 2, it will be seen that an opening 92 is providedin a part of the exterior wall 80 of the shroud 76, and that thisopening 92, which is defined by oppositely facing end surfaces 94, 96 ofthe wall 80 includes means in the form of a movable shield 98 forprotecting the articles 32 against contamination which might enterthrough the opening 92. The shield 98 is adapted to be removablyreceived in a relatively snug relation within the opening 92, that is,with the edges 100, 102 of the shield 98 engaging the end surfaces 94,96. Means in the form of pins 104, 106 are provided for locating theshield 98 and for establishing the path of movement thereof in a mannerwhich will be described in greater detail herein. As shown in thephantom lines in FIG. 2, the shutter or shield 98 may be moved from theclosed position to an open position'lying closely along the outersurface of the wall 80, thereby exposing the articles 32 to anyparticles which may be sputtered from the target assembly 108 receivedin a target housing portion 110 of the chamber 14.

Referring again to FIG. 1, it is shown that each wall 80, 83 comprisesrespectively an outer surface 112, 114, an inner surface 116, 118, andintermediate heater units 120, 122, the construction and function ofwhich will be described in further detail herein. Referring now toanother principal portion of the cleaning and coating ap paratus 10, itwill be seen that the target assembly 108 includes a dark spaceshielding assembly 124, a target plate 126, and a backing plate 128which will be described in further detail herein. A co-axial lead-inassembly 130, details which will be set forth further herein, extendsthrough a rear wall portion 132 of the housing portion 110.

Referring now to FIG. 9, the construction of one form of the shield 98and its associated operating components are shown. Thus, FIG. 9 showsthat a support arm 134 is fixedly attached to the rear surface 136 ofthe shield 98, and the support arm 134 includes a driving gear sector138, a pair of elongated slots 140 receiving respectively a guide pin142 and a guide and pivot pin 144. Teeth 146 are arranged on the sector138 so that rotation of the shaft 148 and its associated driving gear150 will move the arm 134 straight forward a given distance as shown inthe phantom lines, until further rotation of the gear 150 will cause aswinging of the shield 98 to the fully opened position shown in phantomlines in FIG. 9. Reversing the direction of the shaft 148 and itsassociated gear 150 will cause the shield 98 to swing back to itsoriginal extended position and then be retracted to a position whereinthe opening 92 defined by the end walls 94, 96 of the outside wall 80 isclosed. Suitable insulators (not shown) are provided for insuring thatthe shield 92 and its associated mechanism are of the same electricalpotential as the remaining portions of the shroud assembl 76.

Referring now to FIG. 3, additional details of the leadin assembly 130,the target assembly 108 and certain of the electrical components areshown. The backing plate 128 contains a continuous tube 152 having thenear end thereof communicating with the interior passage 154 of an outercoolant tube 156, inside which is co-axially disposed an inner coolanttube 158, the interior 160 of which communicates with the far end of thetube 152. Water or like coolant passes in the direction of the arrows,that is, into the backing plate 128 of the target assembly 108 throughthe outer tube 156 and thence circuitously through the tube 152 withinthe backing plate 128 and out the exit opening 162 of the inner tube158.

A wire lead 164 is attached to the outer surface of the outer tube 156,which serves as the connection to the radio frequency generator, shownschematically at 166. A ceramic insulator 168 and gasket assembly 170are provided to provide electrical and vacuum insulation, and, beingconventional and not forming per se a novel part of the presentinvention, further description thereof is omitted. The target plate 126is disposed in electrical as well as intimate heat exchange contact withthe backing plate 128, and typically in a pure chromium metal or othermetal or alloy to be deposited on the article or substrate. The backingplate 128 is preferably copper or other like electrically and thermallyconductive material. The dark space shielding assembly 124 surroundsthese components in the illustrated manner.

Again making reference to FIG. 3, a direct current (DC) supply 172 isschematically illustrated for connection at a terminal 174 to a movablepole 176 of a switch 178 so that, in one position of the switch 178,communication may be established between the direct current source orsupply 172, which has one terminal thereof grounded, as by lead 180, andthe article 32 to be coated. A radio frequency (RF) supply 182 having agrounded lead 184 on one terminal thereof has an opposite terminal 186connected to a lead 188, so that connection may also be establishedbetween this supply 182 and the articles 32. Another terminal 190 isgrounded by lead 192 so that the articles 32 may be grounded by movingthe switch 178 to an appropriate position. Means in the form of a lead194 are provided for grounding the shield 98 through the switch 196 ifdesired. As the description proceeds, it will more clearly appear that,in some embodiments, the RF generator 166 and the RF supply 182 may bethe same unit, and may be different units in other embodiments. At anyrate, FIG. 3 shows that an RF connection may be established between thegenerator 166 and the target and backing plate 126, 128, that the shield98 may or may not be grounded, and that the blade or other articles 32may alternately be floating, grounded, or connected to a DC supply or toan RF supply, as desired. The exact connections and the sequences inwhich they are made will be set forth below in connection with adescription of the operation of the apparatus.

Referring now to FIG. 4, there are shown somewhat schematically a vacuumchamber 198, having a target electrode 200 therein, in a spatiallycommunicating relation with an inert gas source 202 by means of a leakvalve 204 disposed in the connector line 206, and in electricalcommunication or contact with the tunable RF renerator and amplifierassembly 208 and the tunable pi matching network 210, through thecoaxial lead-in assembly 130. These components, the construction andarrangement of which are generally known to those skilled in the art,will be described briefly, although the detailed construction featuresof these elements do not per se form a novel part of the presentinvention.

Thus, the tunable generator and amplifier assembly 208 is schematicallyshown in the form of lead 212 adapted for connection to an oscillator orother radio frequency source (not shown), and a tube 214 which isconnected thereto so as to amplify the RF signal to the desiredintensity, an inductor 216 and a pair of grounded variable capacitors21-8, 220 being connected to either terminal of the inductor 216 forestablishing a resonant condition of the electrical circuit, typicallyat a frequency of 13.56 megacycles. The pi matching network 210 includesa grounded fixed capacitor 222 and a variable capacitor 224 in parallelwith each other, and further includes an inductor 226 and a secondvariable capacitor 228 between the inductor 226 and the target electrode200. The matching network 210 is adapted to match the impedance of theoutput circuit, including the amplifier tube 214 and its associatedcircuitry with the impedance of the target electrode 200. In otherwords, the target electrode 200, which is isolated from the ground,together with its inductor 226 and variable capacitor 228, is an opencircuit to direct current but has a definite AC impedance at a givenfrequency, and this impedance is matched in the manner shown, or in another suitable manner, to the impedance of the output circuit furnishingthe signal. Typically, the output circuit has a 50 ohm impedance, andthe target assembly should be tuned so as to have the same impedance.The capacitor 228 also serves to couple the output circuit to the targetelectrode 200 capacitively, so that direct current bias may be built upon the target electrode 200.

Referring now to FIG. 5, the connection between the DC supply 172 andthe articles 32 are shown, it being apparent that the blade is separatedby a high vacuum gap 230 from a grounded element 232, which is shown asbeing disposed parallel to the edges 66 of the blade or other articles32. Thus, as will be described in further detail herein, under properconditions, a glow discharge may be developed in the space 230 betweenthe grounded element 232 and the blade 32, in the presence of a minuteamount of inert gas leaked into the space 230 over a background of veryhigh vacuum (low pressure), and ionized by high energy current flow.

FIG. 6 shows an RF supply 182 connected to the article 32 and also showsthe grounded element 232 being spaced apart from the articles 32, andwith the edges 66 of the articles 32 and the element 232 being generallyparallel. As will be described further herein, a reverse sputtering orsputter etching may take place under these conditions if an inert gas isleaked in minute quantity into the space 230 between the article 32 andthe element 232, over a background of high vacuum, and ionized.

Referring now to the operation of the embodiments of the invention shownin FIGS. 1 and 2, the articles 32 to be coated are razor blades, and theprocess may be carried out as follows.

EXAMPLE 1 The vacuum tight housing 14, including the roof portion 88thereof, is lifted vertically from the base 12, and a plurality of razorblades 32 are disposed in a stack in parallel relation to each otherwith the central apertures thereof in registry with the tines 42 on thebayonet assemblies 30. Each bayonet assembly 30 is loaded with a stackof blades, with each stack containing up to several thousand blades.When all the bayonet assemblies 30 are fully loaded and inserted withthe holder members 44 thereof in position of use, the housing 14 isaligned and placed over the base 12, so that the blades are surroundedby the shroud 76 in the manner shown in FIG. 1.

Thereupon, a roughing vacuum pump (not shown) is operated to draw aninitial vacuum inside the unit 10, and thereafter, the vacuum isincreased to a level approximately 1 10- millimeters (mm.) of mercury(torr). The shield 98 is moved to the closed position so that twocontinuous inwardly facing surfaces 116, 118 are presented to theblades. As shown in FIG. 5, the shroud assembly 76 may be grounded, sothat the element 232 in FIG. 5, in this mode of operation, would be oneor both of the surfaces 116, 118 of the shroud 76. A potential of fromabout 500 to 3000 volts DC, and preferably about 1000 volts is impressedon the blades, such as from the DC source 172. At this point, argon orlike inert gas is leaked through the valve 204 by a source 202 (FIG. 4)until the pressure reaches a level from about 1 10- to 1 10 torr. Underthese conditions, a current of about 500 milliamperes (ma.) will bedeveloped, and the resulting glOW discharge will cause ionization ofargon atoms and impingment thereof onto the blade edges to a degreesufficient to remove surface contaminants, particularly organic materialand adsorbed gases. Preliminary vaporization of such volatilecontaminants, and elimination of adsorbed material may be aided byactivating the heater units, 120, 122 so as to heat the blades 32 to atemperature well below their annealing point, but high enough to aid inremoving these contaminants. Typically, the blade edges may reach atemperature of 300 to 400 F.

After the glow discharge has proceeded for one or two completerevolutions of the ring 28, which might typically take three to sixminutes or more, the DC supply is disconnected from the blades orarticles 32, the ground connection to the shroud 76 is removed so thatit is insulated from the ground, and the ring 28 and associatedcomponents, including the articles 32 are then grounded. The vacuum isthen again reduced to the level of about 1 l0- torr as a backgroundpressure, RF energy at 13.56 megacycles or megahertz (me. or mHz.) issupplied to the target electrode 126, and argon is leaked through thevalve 204 until a pressure of approximately 6 to 9X10- torr is reached,while the shield 98 remains in the closed position. The electrode 126becomes the cathode in this mode of operation, and the argon or otherinert gas atoms which are ionized in the RF field are attracted to thetarget 126 by the DC bias thereon with consequent sputtering of surfaceatoms from the target 126. The major portion of these sputtered atoms ofcoating material fall on the outer surface of the shield 98, which isinterposed between the articles 32 and the target 126. After a minute ormore of operation in this mode, the surface of the target 126, whichwould normally have contained a certain amount of contamination such asoxides, adsorbed gases, or the like will become completely clean andpure, free from any contamination. Thereupon, the shield 98 is moved tothe position shown in phantom lines in FIGS. 2 and 9, and as the ring 28continues to rotate, each blade or article passes by the target 126 withits edges 66 generally parallel thereto and in a facing relation to thetarget 126. After each bayonet assembly 30 has passed the target 126twice, both edges of the articles 32 contained thereon have been exposedfor coating for the desired time, and the coating operation is complete.

Thus, it will be seen that the apparatus and method just describedprovides means and methods for glow discharge cleaning under vacuumconditions to clean the surface of the articles to be coated, followingwhich the articles are protected during vacuum cleaning of the target,whereupon the final step of coating the clean blades with materialdeposited from the cleaned target is accomplished. All of these stepsare carried out in the same apparatus, merely by changing electricalconditions and manipulating the vacuum level and inert gas leak valvecontrols, but without exposing the articles to any atmosphericcontamination by breaking the vacuum during any of the operationalcycles. The blades cleaned and coated by the use of this method andapparatus have proved to be outstanding in coating integrity anduniformity.

The same apparatus, or a different but similarly constructed apparatusmay be used in a somewhat different but related mode of operation, aswill now be set forth.

EXAMPLE 2 A method was performed as set forth above, differingsignificantly only in the respects set forth below. Following loading ofthe articles within the apparatus and establishment of the describedvacuum, articles 32 were connected to an RF supply such as the supply182, having one terminal thereof grounded, and the other terminal 186thereof in electrical communication with the bayonet 30 and the articles32 contained thereon. The shield 98 remains in the closed position, andthe shroud assembly 76 may be grounded. Argon or like inert gas isleaked through the valve 204 to establish a pressure of about 1 to 3 10-torr. The blades, at a power setting of the RF supply sufficient tocause a current flow of about 50 ma., achieve a DC bias of up to about3000 volts, and as the argon ionized atoms bombard the blade edges, anyoxide layer thereon, and small amounts of the metal surface itself, areremoved by this bombardment, to insure that the blade surface to becoated is completely free of contamination, including atmosphericcontamination.

After several minutes, the cleaning operation, which can becharacterized as reverse sputtering, that is, using the intendedsubstrate or article as a target, is complete. Thereafter, the RF supplyis connected to the target 126, the blades or articles 32 areelectrically grounded, and the surface of the target 126 is cleaned inthe manner set forth in connection with 'Example 1. Thereafter, theshield 98 is moved to the open position, and the blades or otherarticles 32, which are at ground potential, are coated, also in the samemanner as set forth above in Example 1. The blades cleaned and coated bythe use of this method and apparatus have also proved to be outstandingin coating integrity and uniformity.

EXAMPLE 3 Blades were cleaned and coated in the manner set forth inExample 2, except that a cleaning operation, in this case ischaracterized as a sputter etching operation, instead of reversesputtering. This operation was accomplished by applying approximately1000 watts of RF power at 13.56 mHz. to the blades, which attained a DCbias of from about 4000 to about 5000 volts. Cleaning was carried outunder an argon pressure of from about 6 to about 9 10- torr, for aperiod of several minutes. In this mode, less argon or other inert gaswas used than in the foregoing examples, and the distance between theblade or other articles 32 and the grounded terminal is preferablysomewhat greater than under the conditions set forth in Example 2. Thisoperation may be suitably carried out in an apparatus in which theshroud 76 has the walls 116, 118 thereof spaced farther from the edges66 of the articles 32 than would be the case where glow dischargecleaning is used. The target cleaning and blade coating is carried outin the same manner as in the foregoing Examples 1 and 2. Excellentresults were obtained.

EXAMPLE 4 An apparatus substantially the same as that described abovewas used to carry out the following method of the invention, in whichthe blades or other articles 32 were cleaned and coated simultaneously.In this case, the inner surfaces 116, 118 of the outer and inner walls80, 82 of the shroud 76 were made with a substantial thickness ofarticle coating material thereon, that is, typically, with a relativelythick coating of pure metallic chromium thereon. Blades were loaded inthe manner set forth in the above examples, and the shield 98 was movedto the closed position. An RF supply 234, having one terminal 236thereof grounded, has the other terminal 238 thereof connected, as by aswitch 240, to the inner surface 116, 118 of the shroud 76, and to theinner surface 136 of the shield 98. An RF supply such as the supply 182is connected to the ring 28 and thus to the bayonet 30 and the articles32 supported thereon. The RF supply may be a single unit having one leadattached to the shroud 76 and the other to the articles 32, or twoindividual RF supplies, one for the shroud and one for the articles, maybe used.

After connections have been made as set forth above, the interior of theapparatus 10 is evacuated to a background pressure of about 1x10- torr,and the walls 116, 118 of the shroud 76 are supplied with a 13.56megacycle RF, the shroud 76 being electrically isolated, as by theinsulator 86, from the ground. A power of about 5000 watts is appliedand a voltage of about 5000 volts DC may be developed as argon is leakedthrough the valve 204 until a pressure of about 6 to 9X 1O is reached.The blades or articles 32 to be coated are also supplied with an RF ofthe same frequency, and the insulator 20 or the like insures that thering 28 and parts of the apparatus 10 operatively associated therewithare isolated from the ground. A power of from about 800 to 1000 watts issupplied to the blades, which develop a DC bias of about 2000 volts. Inthis circuit the articles 32 or blades form one electrode of one RFsupply and the ground the other electrode. In the other RF circuit, theshroud 76 forms one electrode, and the ground is the other electrode.Under the above conditions, the ionized inert gas atoms will strike boththe DC biased articles 32 and the target, which in this case comprisesthe interior surfaces 116, 118 of the shroud 76. However, since agreater bias is developed on the target than on the articles, moresputtering will take place at the target than on the articles, forexample, in the relative ratio of from about 2 to 1 up to about 10 to 1,preferably between 2 to 1 and 3 to 1. In this manner, the surface of thearticles will be cleaned by a reverse sputtering or sputter etchingprocess while target material is sputtered onto the article at a greaterrate than sputtering therefrom takes place. Any contamination of eitherthe target or the blade will thus become diffused rather than remainingin one or two, near surface layers, and, since a thickness of 10 to 30atomic diameters of surface coating is ultimately built up on the bladeor other articles, such contaminants, even if present, do not damage thequality or integrity of the coating. In this case, a certain incidentalamount of coated material is resputtered back to the target, but theoverall effect is that of simultaneously reducing the target thicknessand placing a high quality coating on the articles.

Although it is not necessary that the two RF circuits be in exactresonance, the frequencies should be as nearly the same as possible.This is not ordinarily a problem, however, since a crystal oscillatorhaving a definite, fixed frequency is commonly employed for generatingsuch RF signals for amplification. In this case, vacuum and electricalconditions are maintained the same as from the outset of the process,until completion of the coating. Thus, this form of the apparatus alsohas all the advantages of the methods set forth in Examples 1 through 3above, although the particulars of the apparatus and method are somewhatdifferent. In this embodiment, the shield 98 need not be movable, andthe target assembly 108 and the housing may be eliminated, although itis possible to operate the apparatus in the form shown herein accordingto the method described in this example, the target and housing notbeing functionally involved, but not being required to be removed foroperation. Thus, with the proper electrical connections, the apparatusillustrated herein may be used in these different modes of operationwithout alteration, or an apparatus according to the invention may beconstructed so as to be useful in all modes but to favor a particularmode of operation 1n use.

Referring now to FIGS. 7 and 8, portions of another form of theapparatus of the invention are shown, these elements being adapted toreceive a plurality of articlesupporting elements thereon for handlingin a manner and for purposes which will now be set forth.

Referring now specifically to FIGS. 7 and 8, a cam track assembly 242 isshown to include a circular continuous cam body 242 having an outersurface 246 adapted to guidingly receive thereon a front bayonet drivepin 248 and a rear bayonet drive pin 250, each pin 248, 250 beingoperatively associated with an article holder 252. A second, outer camelement 254 for effecting rotation of each of the holders 252 about itsaxis is disposed on a ring and cam support plate 256 which also supportsthe body 244, with the profiled inner surface 258 of the element 254facing a complementary shaped outwardly facing surface 260 on the body244, and spaced apart therefrom by approximately the diameter of a pin248 plus a slight working clearance.

Referring now to FIG. 8, the disposition of the pins 248, 250 betweenthe surface 260 of the cam body 244 and the inner surface 258 of theouter cam element 254 is shown. As further shown in FIG. 7, the two pins248, 250 ride with their inner surfaces in a sliding relation to theouter surface 246 of the cam body 244, thereby maintaining the holders252 and any articles disposed thereon substantially in a fixedorientation with respect to the circular body 244. That is, for example,the articles are supported so that a line extending between the pins248, 250 would always be substantially perpendicular to a radius of acircle disposed co-axially with relation to the cam body 244. Assumingthe holders 252 to be in circular motion in the path defined by thesurface 246 of the cam body 244, as the pair of pins 248, 250 are movedcounterclockwise as shown in FIG. 7, a point will be reached where theleading pin 248 engages the nose portion 262 of the cam element 254,thereby causing the lead pin 248 to be moved inwardly and therebycounterclockwise about the axis of the holder 252, that is to the leftas it is moved between the surfaces 258, 260 which define a channel 264.Since the holder 252 is rotated about its own axis, the trailing pin 250is moved to the right of a motion line parallel tto the outer surface246 of the cam 244. Thus, this pin 250 rides along or outside of theouter surface 244 of the cam element 244, while following the profile ofthe cam channel 264 causes the lead pin 248 to begin lagging behind inrespect to the trailing pin 250 as the holder 252 continues movement,until their positions are reversed, as shown in FIG. 7 where the pins248, 250 are emerging from the channel 264 and passing the end of thecam element 254 in FIG. 7. Thus, a holder 252 will maintain anorientation with a part of the articles mounted thereon facing inwardlytoward the center of the cam track 244 for about 300 to 330 ofrevolution, for example, after which, by engagement with the cammechanism just described, it will rotate one-half turn about its ownaxis to present an opposite face of a supported article to the side, ortoward the center of revolution.

Referring now to FIG. 8, other portions of the mechanism, includinganother form of the means for supporting and rotating the articleholders Within the apparatus as well as about their own axes, are shown.As seen in FIG. 8, each article holder 252 includes a lower extensionportion 268 held by a fastener 270 in fixed relation to a base 272,which includes openings 274 for for receiving the pins 248, 250. Abearing assembly 276 locates the holder 252 and mounts it and itsassociated components for rotation about its vertical axis. A snap ring278 retains the bearing assembly 276 in position within the opening 282in the rotatable ring 282. Fasteners 284, 286 respectively secure aninternally toothed ring gear 288 and a bearing plate 290 to the ring282. The ring and cam support plate 256 supports a lower bearing race292 having a groove 294 therein in which is received a plurality of ballbearings 296 for supporting the plate 290. Another bearing assembly 298on an inner surface 300 of the plate 256 includes a ring driving stubshaft 302 having on one end thereof a pinion gear 304 for engagementwith the ring gear 288, and a bevel gear 306 on the other end thereoffor engagement with a matched driving bevel gear 308 supported on adriven shaft 310. A motor (not shown) drives the shaft 310 through anouter output shaft 312 and a flexible coupling 314. A bearing assembly316 supports the driven shaft 310 and the gear 308 in rotatable relationto the bottom support 318 for the plate 256. An insulator 320 isdisposed between the support 318 and a lower portion 322 of the cleaningand coating apparatus 10.

The operation of this form of article supporting and handling means issimilar to the operation of the form shown in FIGS. 1 and 2, anddescribed in connected with Example. 1.

However, the means for driving the ring 282 are somewhat difierent,comprising the ring gear 288 and pinion gear 304 with its associatedmechanism, instead of the chain 58 and the gears 50, 58 illustrated inconnection with the description of FIGS. 1 and 2.

The resulting motion of the supported articles is different in theembodiment shown in FIGS. 7 and 8 than it is in the embodiments shown inFIGS. 1 and 2, for example. Thus, the provision of the pins 248, 250riding on the exterior surface 246 of the cam body 244 serves tomaintain the edges 322 of any article 316 parallel to an inner surface318 of a shroud or the like 320 and perpendicular to radial planesdefined by the longitudinal axis of the shroud 320 during an entirerevolution of the ring 282, except where the cam track assembly 242 actsto rotate each holder 252 about its own vertical axis. In the embodimentshown in FIGS. 1 and 2, on the other hand, the bayonet assemblies 30were rotated continuously one degree about their own axes for each twodegrees of revolution of the ring 28.

Therefore, the embodiments shown in FIGS. 7 and 8 are preferred where itis desired to maintain an edge 322 of an article 316 parallel to a givensurface 318 so that the potential drop between the edge 322 and thesurface 318 is relatively the same at all points along the edge 322.Accordingly, in some modes of operation, the manner of supporting theblades and manipulating them shown in FIGS. 7 and 8 is preferred.

The above examples have been described generally making reference to thearticles 32 or 316 being double edge razor blades. However, where thearticles are single edge blades, or where only one side of an article isdesired to be cleaned and coated, rotation of each bayonet 30 or holder252 about its own axis is not necessary, and portions of the mechanisms,such as the cam surface 260 and the outer cam elementt 254 may be doneaway with, as might the chain and gear assembly described in connectionwith FIGS. 1 and 2. In such case, it is also obvious that only onesurface of a shroud need be charged if the glow discharge or sputteringwere to take place with respect to only one edge or surface of asupported article.

EXAMPLE 5 A plurality of blades 316 or like articles were placed on theholder 252, and the blades were cleaned by any of the methods set forthin the foregoing Examples 1 through 3, and were coated by sputtering achromium coating from the target 324 disposed within a shield unit 326in the same manner as described in connection with the above Examples 1through 3. The apparatus shown in FIGS. 7 and 8 also operated in amanner just described, that is, with the ring 232 rotating about itsaxis and aligning the plurality of holders 252 such that the edges 322of the articles 316 disposed thereon are kept parallel to the innersurface 318 of the shroud 320 for about 330 of revolution of the ring282, and then rotated 180 about their own axes as set forth above. Theelectrical connections were made in the same manner as set forth inconnection with Examples 1 through 3, and the unit described waseffective to coat razor blades with a thin but continuous, uniformcoating having outstanding integrity and adhesion. The apparatus wasoperative to produce substantially equal results when cleaning waseffected by the glow discharge method, the sputter etching method, orthe reverse sputtering method.

The apparatus described is also operative to produce excellent bladeswhen modified and operated in the manner set forth in connection withthe description of the embodiment of Example 4.

Summarizing the method and apparatus referred to above, it will beparticularly noted that the provision of the shield 98 serves the dualfunction of providing means for shielding the blades or articles againstcontamination during the time the target is cleaned by sputtering thefirst several layers of surface material therefrom, and also thefunction of protecting the target from sputtered contamination duringthe time the blades are being cleaned by glow discharge, sputteretching, or reverse sputtering.

The illustrated apparatus includes support means for the article holdersin the form of the solid rings shown, but it will be appreciated thatthe articles might be moved past the target by other means, such as bymounting the holders on links of a continuous belt or chain, forexample. One sputtered material illustrated herein is metallic chromium,but it will be understood that other metals, metal alloys, and compoundssuch as metal carbides or the like may also be sputtered onto the coatedarticles. In the event that an article is desired to be 13 covered withtwo or more overlying layers or successive coatings following cleaning,it is obvious that additional target means may be provided, suitableconnections may be made to supply high frequency energy to them in anydesired sequence.

A commonly inert gas used in the sputtering operation is argon, butother inert gases such as neon or krypton may also be used. Details ofthe electrical circuitry may be altered by those skilled in the art, buta typical means of establishing a connection between relatively movableparts in a high vacuum is by the use of a gold brush or the like such asthat shown in FIG. 1.

It will therefore be seen, by reference to the foregoing description,that the present invention provides a new and useful article coatingmethod and apparatus having a number of advantages and characteristics,including those pointed out herein and others which are inherent in theinvention.

We claim:

1. In a method of cleaning a plurality of cutting instruments eachhaving at least one cutting edge and of depositing a thin continuouscoating on the cutting edges; wherein said method is performed in asputtering chamber comprising at least one target having a coatingmaterial thereon, shroud means for enclosing said instruments comprisinga pair of spaced concentric cylindrical inner surfaces having alongitudinal axis, and shutter means for opening said shroud means toexpose the cutting edges of said instruments to said at least onetarget; the steps comprising:

(a) disposing said cutting instruments in a plurality of arrays withinsaid shroud means, each of said arrays having the instruments thereinarranged with the cutting edges parallel to said inner surfaces andperpendicular to a radial plane passing through said longitudinal axis,

(b) evacuating said chamber,

() establishing an electrical potential difference between said shroudmeans and said arrays,

(d) moving said arrays between said inner surfaces in a circulardirection while maintaining the relative array arrangements of step (a),

(e) introducing minute quantities of an inert gas into said chamber toclean the cutting edges by removing atoms therefrom,

(f) establishing an electrical potential difference between said atleast one target and said arrays, and

(g) actuating said shutter means to open said shroud means andsequentially expose said at least one target to each of said arrays,thereby sputtering said coating material to the cutting edges of saidinstruments.

2. A method as defined in claim 1 further including the step of cleaningsaid at least one target by removing a portion of the surface thereof bysputtering prior to p (e)- 3. A method as defined in claim 1 in whichsaid at least one target is cleaned of surface contamination bysputtering prior to step (g).

4. A method as defined in claim 1 wherein step (0) includes applying adirect current bias to said arrays.

5. A method as defined in claim 1 in which step (c) includes applying ahigh frequency alternating current to said arrays to establish a directcurrent bias on said arrays with respect to ground.

6. A method as defined in claim 1 in which said atoms removed from thecutting edges in step (e) include atoms of organic contaminants andatoms of gases adsorbed on said surface.

7. A method as defined in claim 1 in which said atoms removed from thecutting edges in step (e) include portions of the cutting edges andatoms of oxide coatings formed on the cutting edges.

8. A method as defined in claim 1 in which said coating materialcomprises substantially pure metallic chromium.

9. In a method of cleaning a plurality of razor blades each having atleast one cutting edge and of depositing a thin continuous coating onthe cutting edges; wherein said method is performed in a sputteringchamber comprising at least one target having a coating materialthereon, shroud means for enclosing said blades comprising a pair ofspaced concentric cylindrical inner surfaces having a longitudinal axis,and shutter means for opening said shroud means to expose the cuttingedges of said blades to said at least one target; the steps comprising:

(a) disposing said blades in a plurality of arrays between said innersurfaces, each of said arrays having the blades therein arranged withthe cutting edges perpendicular to a radial plane passing through saidlongitudinal axis,

(b) evacuating said chamber,

(c) establishing an electrical potential difference between said shroudmeans and said arrays,

(d) moving said arrays between said inner surfaces in a circulardirection while maintaining the relative array arrangements of step (a),

(e) introducing minute quantities of an inert gas into said chamber toclean the cutting edges by removing atoms therefrom,

(f) establishing an electrical potential difference between said atleast one target and said arrays, and

(g) actuating said shutter means to open said shroud means andsequentially expose said at least one target to each of said arrays,thereby sputtering said coating material to the cutting edges of saidblades.

References Cited UNITED STATES PATENTS 3,458,426 7/1969 Rausch et al.204-298 3,021,271 2/1962 Wehner 204-192 3,121,852 2/1964 Boyd et al.204-192 3,324,019 6/ 196 7 Laegreid et al. 204-192 3,451,912 6/1969Dheurle et al. 204-192 3,480,535 11/1969 Bloom 204-192 3,479,269 11/1969Byrnes et al. 204-192 3,515,663 6/ 1970 Bodway 204-192 3,528,906 9/1970Cash et al. 204-192 3,562,140 2/ 1971 Skinner et al. 204-192 JOHN H.MACK, Primary Examiner S. S. KA NTER, Assistant Examiner US. Cl. X.R.1204-298

